Read through a few random posts to see issues people have with Warzone.
Modern Warfare (2019 version) and Warzone share an engine. This is the most up to date and efficient engine in FPS today. While there are problems in the engine, the benefits and overall performance of it outweighs those issues and exceed anything else on the market.
That said, there are 2 glaring issues with Warzone. PC Hacking, and CPU hog. Some people mentioned it not being optimized and not able to run on a 970/980 gpu. The fact is, on low settings it should run just fine at 70+ FPS on those GPUs and look good. However, it gets bottlenecked by CPUs. It renders shading and textures off the GPU but runs the engine off the CPU. This is where it causes issues for older systems. The download sizes are massive but they are making it better. They are also adding in so much new free content on Dec 16, and i don't expect it to grow much larger than a gigabyte or so for all that new content, as they have been prepping it.
The PC hacking tho, It just frustrates that it hasnt been fixed yet.